Processing of laterite ore

Abstract

A process for the leaching of metals from highly oxidized laterite ores. The ore is admixed with an acidic aqueous medium, preferably a solution of sulfuric acid and the resulting mixture is treated with a sulfur reducing agent so as to reduce mineral species containing cobalt, nickel or manganese. The sulfur reducing agent may be an aqueous solution of sulfur dioxide or more preferably the sulfur dioxide is generated in situ by the reduction of alkali metal sulfite salt. The process is conducted at ambient temperature and pressure with the reduced mineral species being dissolved and subsequently recovered.

1 . A process for leaching metals from highly oxidised laterite ores comprising admixing the ore and an acidic aqueous medium and treating the resulting mixture with a sulfur reducing agent so as to reduce mineral species containing cobalt, nickel or manganese, the reduced mineral species being dissolved and subsequently recovered, wherein the process is conducted at a temperature of from 20 to 50° C. throughout, a pressure of less than 2 atmosphere throughout, and within a time frame of 20 minutes to 20 hours. 
   
   
       2 . The process of  claim 1 , wherein the time frame is 30 minutes to 10 hours. 
   
   
       3 . The process of  claim 1 , wherein the highly oxidised laterite ore contains asbolane. 
   
   
       4 . The process of  claim 3 , wherein the highly oxidised laterite ore comprises cobalt in the range of 0.1 to 10 percent by weight and nickel in the range of 0.1 to 20 percent by weight. 
   
   
       5 . The process of  claim 4 , wherein the highly oxidised laterite ore comprises cobalt in the range of 2 to 5 percent by weight and nickel in the range of 5 to 15 percent by weight. 
   
   
       6 . The process of  claim 1 , wherein the sulfur reducing agent is provided in the form of an aqueous solution of sulfur dioxide. 
   
   
       7 . The process of  claim 1 , wherein the sulfur is generated in situ by the reduction of alkali metal sulphite. 
   
   
       8 . process of  claim 7 , wherein the sulfur dioxide is generated in situ by the reduction of sodium sulfite. 
   
   
       9 . The process of  claim 6 , wherein the amount of sulfur reducing agent is supplied in the range of 0.8 to 3.2 mol SO 2 /kg of the ore. 
   
   
       10 . The process of  claim 6 , wherein the amount of sulfur dioxide is supplied relative to the weight of the ore by adding a controlled amount of sulfate salt, to selectively dissolve nickel, manganese and cobalt with minimal leaching of iron from the ore. 
   
   
       11 . The process of  claim 10 , wherein the sulfite salt added is in the range of 10 to 40 percent by weight of the ore. 
   
   
       12 . The process of  claim 1 , wherein the pH of the aqueous medium is less than 2.0. 
   
   
       13 . The process of  claim 1 , wherein the ore is crushed to a size in the range of 50 to 600 mesh. 
   
   
       14 . The process of  claim 1 , wherein the ore is crushed to a size in the range of 50 to 600 mesh. 
   
   
       15 . The process of  claim 14 , wherein the ore is crushed to a size in the range of 90 to 110 mesh.